The objective of all emails is to communicate. The writer needs the recipient to understand. So s/he should make it as easy as possible for the recipient to understand the message. The writer is writing the email, not the recipient, right? It is the writer's job to write it well, not the recipient's! But often the recipient has to spend a long time and work very hard to understand a message. (This is not just a question of language.) Basically, sending "bad" emails shows no respect for the recipient and is not polite. The writer does a little work and the recipient does a lot of work.
So here are 5 tips on sending emails the best way possible, and making life easier for everyone.